Computer Network is a group of computers connected with each other through wires, optical links so that various devices can interact with each other through a network. Computer network is for sharing of resources among various devices .There are different models in computer networking :*OSI model *TCP/IP model.
There are seven layers in OSI model.
1.Physical layer : this layer provides a physical medium through which the bits are transmitted.
Functions of physical layer are: line configuration, data transmission, topology, signals.
2.Data link layer: it is used for error free transfer of data frames.
Functions: Framing, Physical addressing , Flow control, access control.
3.Network layer: it is responsible for moving packets from source to destination.
Functions: Internetworking, Addressing, Routing , packetizing.
4.Transport layer: it provides reliable reliable message delivery from process to process .
Functions: Service-point, addressing, segmentation and reassembly, connection control, error control.
5.session layer: it is used to establish, manage and terminate the sessions.
Functions: Dialog control, Synchronization.
6.Presentation layer: it is responsible for translation , compression and encryption .
Functions: translation, Encryption, Compression.
7.Application layer: This layer provide the services to the user.
Functions: File transfer, access and management(FTAM), mail services.